Check DNT header for service worker's update checking

This CL adds a test to verify if DNT request header exists in a request for
update checking.

Bug: 972458
Change-Id: I58da5ce2bea9d952de2784548c6ca8a32ff9565a
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1669132
Commit-Queue: Makoto Shimazu <shimazu@chromium.org>
Reviewed-by: Matt Falkenhagen <falken@chromium.org>
Auto-Submit: Makoto Shimazu <shimazu@chromium.org>
Cr-Commit-Position: refs/heads/master@{#671581}
2 files changed